Power supply going?

December 13, 2004 6:19 AM

Power supply going? My desktop makes noises that sound like the fan speeds up then slows down. Sometimes as often as 3 times in a minute. I tried switching wall outlets, still with the same surge protector, though. Nothing else plugged in to that surge protector seems to waiver. The desktop is about 2.5 years old, used all day everyday. Is it the power supply? and if so, how difficult is replacing it, and would I have to re install a bunch of shit?
posted by yoga to computers & internet (15 comments total)

Assuming it's a standard desktop, the ps should be relatively easy to replace. A few screws and then there's the cable that plugs into the motherboard. As for re- installing stuff, there shouldnt be anything, if you're referring to software.
posted by isotope at 6:41 AM on December 13, 2004

First make sure it acually is the power supply fan.

It could be a cpu fan instead.
posted by srboisvert at 6:47 AM on December 13, 2004

Or a case fan, which are usually meant to speed up and slow down, but is now making a bit more noise than usual so that you notice it. Is the power supply hot to the touch? Is the CPU heatsink?
posted by mendel at 6:52 AM on December 13, 2004

Um, nothing feels hot, but I haven't pulled the case off to see what is where. I think I may have to call the PC doc. :/
posted by yoga at 7:17 AM on December 13, 2004

Well consdering you use it all day every day like I do I'd say the Power Supply is the safe bet. If you put your ear to the back of the computer you should be able to tell if it is or not. Also, put your hand back there and see if you feel it's air. Like mendel said, is it hot back there?

If it slows down or stops, sometimes if you lightly tap where the powersupply is it starts back up again, then you'll know.

The way I was able to tell when my CPU fan finally went out was my computer would restart when it got too hot. Never made a noise like the powersupply did.
posted by freudianslipper at 7:17 AM on December 13, 2004

You're probably right about the power supply. They're fairly easy to replace. Don't go opening it up though, there is potentially a lot of charge built up in the capacitors, which you wouldn't want to risk unloading on yourself.
posted by knave at 7:29 AM on December 13, 2004

windows box? open the task manager and look at the CPU load. if you see the load spike at the same time as the fan revs up, it might just be a case fan that revs up as load increases. the reason for the random spikes would be something you'd have to hunt down (look at processes and see what's hogging the CPU time).

if the fan speed doesn't match CPU load it is likely to be the power supply rather than the case. should help you narrow it down a bit anyway without having to open it up.

if you have no issue with the power supply fan, look at the CPU fan: some systems have a case fan, plus a big fan housed in a shield that does nothing but suck air over the CPU. if this one is the issue, it can be replaced... i think new case-mounted fans are only about $5 or so. might be cheaper to DIY than to have a tech look at it, as $5 and a few minutes of work cost less than $50/hour plus parts...

don't forget to check for fans on the graphics card... some of these can be replaced if they get bad.
posted by caution live frogs at 8:18 AM on December 13, 2004

If you don't mind the danger of opening up a PSU (so many stories of people hurt, yet I've managed to never harm myself yet), you can re-grease the fan instead (or just replace it). Most of the danger in the PSU lies on the terminals of the large capacitors. This are neatly tucked in on the OTHER side of the PCB, so if you don't remove that, you minimize the danger.

Now, most PSU fans are standard 8 cm case fans. If you want to replace it, match up the colours of the wires, cut, solder, electrical tape (or better yet heatshrink) and you're done.

If you want to re-grease the bearings, it's not tough. Remove the fan, take off the sticker in the center of it. On that size of fan, you'll notice a rubber plug covering a large hole in the center. Remove the plug and fill that hole with some good household / light machine oil (you could use 3-in-1 oil), not degreasers like WD40. Spin the fan rapidly by blowing compressed air through it. Now clean all the dirt particles that are in that fresh oil up with a cotton swap. Add fresh oil again, close the hole up with the rubber plug, clean it up and seal it off with some electrical tape. Your newly regreased fan should be good for about another 2 years from my expereience (I've done this several times).
posted by shepd at 8:42 AM on December 13, 2004

One more thing, while you have your power supply open, check to see if you notice any capacitors that have rounded tops with brown crusties on them. If you notice this, you should throw the power supply away immediately, or at least fix the popped capacitors. It will eventually blow up and ruin your computer if you don't. This was a problem back a couple of years ago...
posted by shepd at 8:44 AM on December 13, 2004

The desktop is about 2.5 years old, used all day everyday. Is it the power supply?

Most definately yes.

...and if so, how difficult is replacing it, and would I have to re install a bunch of shit?

Very, very simple. You'll have to make sure you get the same physical size power supply (they come in a couple of general sizes, one for desktops and the other for towers) and make sure the connector is the same (it's almost certainly ATX).

If you have a proprietary manufacturer's computer case (Compaq is notorious for this) the case might not be easy to open. However, it's usually nothing more than 4 Philips-head screws. The power supply will have one main connector going to the motherboard, this will be a larger cable. Then there will be separate connectors to each of the peripherals (called MOLEX connectors -- they're 4-pin, about an inch wide, and have notches on one side).

Things that need power: CDROM, hard drive(s), floppy drive. Unless you're running some super-fancy system, which it doesn't sound like, any power supply you get will have enough power connectors for all your peripherals.

Please, please buy a good power supply. Most people go to NewEgg or the like and buy the cheapest, most underpowered supply they can find. This is stupid. A decent power supply will cost around $50-$75, and will last for years. A crappy Chinese no-name supply will run you $20, be grossly underpowered, use marginal capacitors, and die a slow painful death. Usually the slow painful death will be pre-empted with numerous "mysterious" system hang-ups that you'll mistakingly blame on your operating system.

Your basic all-around system can get by with ~350W of power, but if you like using tons of USB devices, get a 400W. Antec (True series), Thermaltake, and Enermax are a few good name brands. Read the reviews on NewEgg and you'll be golden.
posted by Civil_Disobedient at 11:45 AM on December 13, 2004

How do I know if the power supply will fit in my machine? It's a Dell dimension 2350 - dunno where that last post went, so sorry if it's a repeat.
posted by yoga at 12:05 PM on December 13, 2004

Epilogue: Turns out Dell is giving me a free power supply as the one I have is still under warranty, miraculously. I've no control over the wattage of the replacement, but free is free and that's good enough for me at the moment. Thanks, all!
posted by yoga at 2:41 PM on December 13, 2004

It always brings a tear to my eye when these AskMe's are resolved in-thread.
posted by Civil_Disobedient at 5:34 PM on December 13, 2004

Funny, I just opened my old box, thinking the CPU fan was going bad, only to discover 3 surprises:
1) CPU fan no problem
2) Motherboard fan dead, but no problems apparent
3) Graphics board had a fan, IT was making terrible noise!

Then I went to the parts store. Fans are readily available here, they tell me. duh? Here?! In South Africa, EVERYTHING is repaired long before replacement. So I head out on my scooter for a more practical shop today.

BTW and FWIW The graphics card is an ATI All-in-Wonder Radeon. I will never buy another ATI product. Crap software, crap drivers, crap fan.
posted by Goofyy at 3:41 AM on December 15, 2004

OOops. They said fans NOT readily available, as must be obvious in context.
posted by Goofyy at 3:42 AM on December 15, 2004